dwchapmanjr

You may want to start a new thread. This one is specific to the 8 speed which has a few lawsuits against it and your issue may get mixed up in that. Frustrating to hear you're having to deal with it. I had to deal with it for 2-3 years on my 8 speed before the new fluid finally fixed it. I'm 2 years out on the new fluid and was hopeful the 10 spd was going to be better. Good thing you got a pico scope done on it. I have never been able to get that done for various vibrations.

Yes, if you have a valve body code they may replace/open it up. 99% of the shudder issue are fixed by either fluid and/or TC replace which doesn't require valve body work/replacement or any tear down. The TC is just a mostly enclosed unit that mounts between engine and transmission and allow power transfer from engine to transmission.

Should be no reason to take out/replace/open up valve body for the TC issue unless you have another unrelated issue like bad transmission fluid temp sensor and you have the one piece harness.

Relatively speaking the TC replacement is pretty non invasive. Engine and transmission do not have to be torn down to replace. TC is just the part that connects engine to transmission. I was definitely concerned about my transmission being town down at my original dealer until I realized it was just a TC replacement.

This is more important than you realize. I purchased my vehicle from a GMC dealer and they had no idea what they were doing with this when it happened. Granted it was early on and PIP5337 was only at D. But they had it 1 week and said it was another 2 week wait time for a tear down of the transmission eventhough they knew about PIP5337D and it did not specify a tear down. Brought it to another dealer. They started with the flush and told me it was a first step and that if it still happened it would likely be a TCC replacement (best information at the time). I eventually got my TCC replaced and it worked for a year. After that they were well aware of the new fluid. Point of the story is you can take it to any GM dealer. Try to find a reputable one that has been there for a while. Talk to the service advisor and ask them about this issue and see how knowledgeable they are about it. Call a few dealers. Some may be a hike. I have 2 dealers on my way to this dealer I go to that would be more convenient.

Oh for sure. I did one of the fronts myself but the fronts do require a little more skill and care. The hardest part about the fronts though were the connector and the pick tool!

Well except for the spring compressor which many people don't feel comfortable using on such heavy duty springs. And if you actually swap the magnetic ride front shocks, the connector can be quite a pain to transfer.

I think it depends on how bad it was and when it was manufactured. If you drove on it a long time with the shudder it probably did start to shred the TCC. I'm nearly 2 years on the new fluid and its the longest its ever lasted without recurring so in my mind it is solved. I have been through 2-3 other fluid changes. My TCC was also replaced early on when they though tit was a manufacturing defect. I'm about 3 years out on the new TCC. During the time they thought it was a manufacturing defect there was some unsubstantiated rumor of it for 2015 and 2016. May be true, may not be.

Mine started about a year after I purchased it and maybe 9k miles, no towing. I imagine in more humid climates its worse of an issue because the fluid will attract more moisture.

Awesome, yeah I'm nearly 2 years in on mine since the new fluid and its been great! I started having this issue when it was first documented as PIP5337A (they went half way up the alphabet on revisions).

Likely my last post. Dealer took it for a drive on a known smooth surface and they could still slightly detect it but said they've just had complaints bout this particular tire type/tread(Bridgestone Dueler H/L Alenza). Said I should likely replace with some Michelin tires the next round. That the tires on there are perfectly balanced but this type of tire has this complaint. Unless I want to cough up $900 or so for a new set, it'll probably be a few years unless this gets worse. Dealer has been reputable and knowledgeable so I believe them and for my sanity (if there's any left), it has gotten good enough to live with (for now). Interestingly with the cold weather and transmission work I had done its better. We'll see how that holds up.

This ended up being the fluid sensor and they replaced the harness and changed fluid due to having to drop the pan. Rides much better and gets up to temp as expected.

My 2015 had the shake about a year in and it took about 2 years for them to find a permanent fix with the new Mobil HP fluid. I went through quite a few flushes and even a TCC replacement but the Mobil HP flush I had done early 2019 fixed it. The issue with the other fluids is that moisture builds up and causes increased friction. You don't mention your mileage but in my maintenance schedule it indicates 45k miles for fluid and filter change which I imagine for a 2018 you're probably close to that.

Sounds like the old TCC shudder - Make sure they're aware of 16-NA-355 - https://static.nhtsa.gov/odi/tsbs/2019/MC-10163890-9999.pdf They'll likely need to flush transmission fluid. If your TCC is shot, procedure is to flush first and see if it comes back and if so likely replace TCC. Around 1250RPM the torque converter doesn't completely lock, its pulsated and light acceleration causes a bit of slippage with the old transmission fluid due to moisture in the fluid. It can also be exacerbated by AFM kicking on and off around the same RPM. You'll get a different shudder when it switches and M7 typically deactivates AFM.

Long history but short of it is long standing vibration seems to be related to tire temperature. 2015 GMC Yukon. New Tires (Bridgestone Dueler HL) 1/31/2020 w/Alignment. They noticed front right strut was leaking and replaced. Vehicle seemed to drive without issue for at least 2-3 months. COVID-19 hit and I hardly drove anywhere for a few months. There was a month span where my truck left the garage only a handful of times. Tires have 3k miles on them despite being 9 months old now. Around July I started driving a bit more and I noticed a pretty bad road vibration and started looking at remaining shocks. Replaced 2 years and it seemed to help as they were leaking and then remaining front strut as it was leaking hoping this would resolve my issue. Took it to the dealer and they road force balanced and rotated, not finding any suspension or tire issues. When I drove away, there was a hard pull to the left. Took it to local shop as I figured it was an alignment but alignment was dead on. They road force balanced and rotated and pull went away. I later found out one of the tires had conicity and was replaced and pull went away. This week in Houston we had a bit of a cold front and I noticed it was driving back to normal, like earlier in the year. Yesterday I was driving around and noticed as soon as the tires started to heat up to 38psi (Cold tire pressure is 35psi), the vibration started to get worse so I pulled over and deflated 2 psi. Next tire got up to 38 and vibration started and I did the same thing and it went away for 10 minutes but came back as the tires seemed to warm up and inflate more due to that. Today I drove trying to reproduce and it seemed to drive better than yesterday and took about 40 mins to get some vibrations that were not even as bad as they have been before. Am I working out some flat spotting? Or is it possible that some tires that have issues that show when they warmed up? Or is it possible I have a suspension issue that slightly under-inflated tires are masking? I plan on going back to the dealer and have them run a picoscope to confirm the source of the vibration and look again. Questions I should be asking them, things I should verify they're checking, etc? This issue has been driving me crazy for months and seems to be going away on its own due to cold temp (55-60F in the mornings, high of 85F) versus the triple digits we were getting in the summer. Looking back at the Jan-March timeframe it would have been around the same temp here so I'm wondering if I'm exposing a temperature related issue with the tires that shows up when the ambient temp is much warmer or the tires have a chance to get hotter. I have the full story documented here before I even thought it might be tire related

Looks like its been about 10 days since I updated. I've been trying to narrow down the vibration. In my search I came across the term NVH or Noise, Vibration, Harshness. GM dealers are supposed to have a PicoScope with NVH module. My service advisor indicated to me that they can do that so when I'm ready to come in, they will. With that said, I wanted to understand it better and documented it in an article I wrote below. Sharing incase it helps anyone else with similar issues. I had an interesting discovery these past few days. In Houston, we've had a bit of a cold spell so my morning drives were a little better. I've noticed my vibration seems to get worse as the vehicle warms up and I drive it for a while. In the morning or cold drives, its almost back to normal. Today I was driving and noticed it started as soon as one tire warmed up to 38psi so I pulled over and deflated it to 36 and it was better for 10 mins. Then the other front tire got to 38 and same thing so I deflated it too and it was better for about 10 mins. I'm not sure if the smoother ride by slightly deflated tires is compensating for something else or if a tire issue is the issue. One of the front tires is brand new though as it had a bad tire pull (tire conicity). Presumably the other front was in the pair with it before being replaced. In any case - if you have too much time on your hands or want to be better equipped to speak to the dealer about vibrations, below will arm you with some tools. I still need to narrow my process down as my numbers are a bit all over the place. I think I have yet to find a great place I can mount my phone to capture the vibrations that is uniform. https://blog.woohoosvcs.com/2020/09/quick-and-dirty-noise-vibration-harshness-quantification/

So a lot of people don't have access to PicoScopes or they don't understand the science behind what it does and how it does it to ask the right questions of the dealer. I wrote this article documenting what I learned going down that path on mine. There are some economical options ranging from a $399 app to a $10 app if you want to do a lot of the manual calculations. I wanted to share incase it helps anyone and their vibration issues. I'm still working through mine now. My regular service advisor at the dealer came back from vacation and followed up with me on an unrelated issue. I asked him if they could do a PicoScope for this issue and he said they could. I'll likely ask for the file so I can view it as the pico diagnostic software is free (in view mode) regardless of their findings. With all of that said, here's my blog of it. I hope it helps someone understand the steps and possibly even diagnosing their own. https://blog.woohoosvcs.com/2020/09/quick-and-dirty-noise-vibration-harshness-quantification/

Ha - I was tempted to but I only have one so I wouldn't want to use it on food again so I just purchased an apparatus to do it. Yeah, I imagine it does. That's probably why the mounting brackets for it are so flimsy/loose, two loose legs on the bottom and rests against a lip on the wall.

I'd be really curious over time how your shift adapts adjust. Interestingly I had my truck in for low temp. It ended up being the harness to my surprise. I thought it was a bad thermostat but they also did a fast relearn. I'm not sure if it common after a fluid flush or because my shift adapts would have learned at a different temperature than expected. Entirely possible such a small temp difference doesn't really matter but it would be interesting to hear from a GM engineer why they want the temps so high.

Watch a few videos, its really simple. Have them do the picoscope and verify the issue was reproduced during it. By default it only takes a 50 second capture. Then have them give you the file. You can download the software and open up the file for free.

Agreed on the fluid, this truck has had fluid flushes/changes about every 8-10k miles of it life (due to the many revisions of PIP5337. Hopefully that equates to the longevity of this transmission. Yeah, I had secondarily asked them to run a picoscope on it but the service advisor was like a deer in the headlights on it. Said he would check it out but then handed over the vehicle once the transmission issue was resolved. He was helping out for my normal one that was on vacation so I may make a dedicated appointment for that if this transmission issue didn't mysteriously fix the shake. I wasn't going to mix the appointments any way so I wasn't frustrated about it. Mine seemed to start when my shocks were failing and after replacing them the issue didn't completely go away. I found an obscure reference in TSB 18-NA-339 ( https://static.nhtsa.gov/odi/tsbs/2016/MC-10135275-9999.pdf ) Condition 6

I like to think I helped a little bit. I pulled the codes, printed them out. Captured the freeze frame of the code and the temp that showed really low and graphs of the transmission fluid temps while driving. I can't take all of the credit though, there are 2 dealerships on the way to this one, one I can almost walk to from my house but I go to the one I do because they've been the best out of the others in the area for service.

To me, I am amazed that electronics and wiring can be submerged in transmission fluid and work properly. I realize this is common place but still amazed me the first time I saw it.

For what its worth, even-though its tangent to the topic. I brought it in and they caught the temp reading -48F. Replaced harness because they detected high resistance and temp hung around 175.

High resistance in the sensor. Replaced and it showed 175 when I took ownership again of it and stayed at 175 most of the way home (highway) although ambient is about 70F right now so its more in line. They did not replace thermostat which based on the temp readings from the dash is fine by me. They did a Fast Relearn on it which always helps the shifting because mine is such a low mileage vehicle it doesn't properly learn all the clutch pressures. Invoice was for $2 shy of $700 but Chevy Protection plan picked up the entire bill, no deductible. I noticed line item 19420015 - "A/TRANS DEXRON VI" when I drove off but when I called he assured me they use the new Mobil 1 Fluid and it is just a generic line item. I'll have to drive it a couple of hundred miles to see if it resorts to its old bad habits, sometimes with my driving patterns it can take up to 6 months. I also had some unrelated road vibration issues that seem to have been gone that I was troubleshooting as a suspension issue.